This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Nowadays, regarding broadcast TV, a broadcaster such as TF1 or M6 in France is not attached to a single broadcast feed. The broadcaster can distribute its live programs simultaneously through several pipes such as Internet Protocol Television (IPTV), or Digital Terrestrial Television (DTT or DDTV), satellite, and even over the worldwide web. One problem is that all these pipes use different network technologies generating very different delivery delays. This may result in a strange user experience such as when a TV spectator is watching a soccer match delivered over his broadband IPTV service and he may hear a joyous explosion from his neighbourhood, reacting to a goal if for example a said neighbourhood is probably watching the same program but delivered through the DTT network. Said TV spectator will see the goal too but it may happen several seconds afterwards. More annoying is the case of interactive programs (e.g. a quiz show) where the competitors (TV spectators located in different homes) are not equally treated depending on their TV feed. Overall the delay difference among all the TV delivery networks is typically several seconds. The broadcaster doesn't wish to handle a complex delivery taking into account the different delivery delays of various used pipes.
A classical delivery system is represented in FIG. 1. It comprises four terminals T1, T2, T3, T4 and a server S connected through four various networks N1, N2, N3, N4 such as for example: Satellite, Cable, digital terrestrial TV, broadband IPTV, on demand, Internet etc. . . . Four Head-ends devices VHE1, VHE2, VHE3, VHE4 are adapted for formatting the content as proposed by the broadcaster (not represented on FIG. 1) for being delivered to said terminals for quasi-simultaneous playbacks. As explained above, there can be delays of about 10 second between the playbacks on standard/basic terminals.
When terminals are not especially adapted for simultaneous playbacks, one will speak of “basic terminals”. Said basic terminals start playing back the delivered content as soon as said content reaches the terminal. But the data delivery durations on the various links, from said server S to said terminals, are not necessarily identical. This variability of data delivery durations introduces delays (up to 10 seconds) between the playbacks performed by all the terminals. This may be problematic when synchronization among terminal users is a strong requirement such as for interactive programs (e.g. TV quiz show wherein terminal users are invited to answer questions in live) or for live events such as a soccer match.
This problem is known and solved by van Deventer et al. in “Advanced Interactive Television Services Require Content Synchronization” appearing in Systems, Signals and Image Processing, 2008. IWSSIP 2008. 15th International Conference, 25-28 Jun. 2008. Van Deventer et al. propose to handle delivery duration variability with synchronization buffers located either in network or at terminals. The proposed solution is not fully described and is silent on the way the modified basic terminal could implement said feature and particularly it is silent on the complexity of the operation for the broadcaster in terms of supplying of synchronisation signals and especially on the problems of deployment of such solution in a world where most of terminals are basic terminals.
One of the goals of the present invention is to propose a solution for synchronizing the rendering of a program delivered simultaneously over different networks which would be simple to manage by the broadcaster in charge of supplying content to various terminals via various networks and last but not least which would be compliant with existing “basic terminals”.